Describe the feature

I couldn't find this type of block in the game and haven't found this as suggestion either. Basically it's a Framed Divided Slope, except instead of being divided vertically like the Framed Divided Slope itself, it'd be divided diagonally over the slanted face.

Framed Divided Diagonal Slope?

It would be useful for inverted pyramid ceilings where you'd want a nice differently colored line along the corners. It's also useful for normal pyramids now that I think about it.

In the attached image you're looking up to a corner of a sloped ceiling. I cannot figure out an other way to make the corner line look nice here.